Valves and, in particular, exhaust gas recirculation valves, used in the exhaust gas region serve the purpose of reducing exhaust gas emissions. Exhaust gas quantities adapted to the particular operating state of the internal combustion engine are thereby returned to the cylinder of the internal combustion engine to reduce environmentally harmful components, in particular, nitrogen oxides. The exhaust gas recirculation valves typically comprise an actuator, which is operatively connected to a valve rod, which is guided via a guide bushing in a housing of the valve and which has, at the end thereof opposite the actuator, at least one control body which corresponds to a corresponding valve seat. Most exhaust gas recirculation valves are designed so that, in the closed state of the valve, the guide bushing is arranged in the region containing fresh air and is separated from the exhaust gas side by the valve closing body. When the valve is opened, i.e., when the valve closing body is lifted off of the valve seat, exhaust gas flows in the direction of the intake manifold, thereby establishing a connection of the hot exhaust gas, which, however, contains soot or is otherwise loaded with caking and adhesive substances, to the actuator housing. The thermal load on the actuator thereby increases since exhaust gas heats the actuator housing and can enter the region of the guide bushing by traveling along the valve rod, whereby deposits form on the valve rod or in the guide bushing, for example, due to temperature differences, wherein the deposits can adversely affect the function of the valve.
In order to avoid this problem, an exhaust gas recirculation valve is described, for example, in DE 103 36 976 A1 which comprises a shielding plate which extends around the valve rod into the channel through which flow occurs so that soot is sheared off the valve rod when the valve rod moves in the direction of the actuator. Penetration by exhaust gas into the guide bushing is also substantially reduced. Protection against thermal loading of the actuator is not, however, disclosed.
An exhaust gas recirculation valve is also described in DE 100 48 499 A1 in which a pot-shaped thermal protection element is arranged between the actuator housing and the flow housing, wherein the thermal protection element extends into an opening of the flow housing and on the base of which an opening for the passage of the valve rod is formed. A peripheral clearance between the flow housing and the thermal protection element exists, however, so that a relatively large surface area for the direct contact of the hot exhaust gas with the actuator housing still remains.
The known embodiments therefore have the disadvantage that a large installation space is required, or a large quantity of heat must be dissipated from the actuator housing, or a housing arranged therebetween, since the actuator could otherwise become damaged by high exhaust gas temperatures that occur.